OK, this might be a shock to some of you.
You're not obligated, legally or morally, to risk your life, limb, or property to save another's, unless you voluntarily accept that obligation.
No, but you are obligated to save someone, if there is no risk involved (e.g. you just have to switch a trigger to turn a machine/electricity off).
No, you're not. No obligation can be created that forces action, without voluntary acceptance of that obligation. I'm obligated not to turn on the switch that kills you, but not obliged to turn on the one that would save you.
To illustrate this, what is the first thing you would say to someone who
had flipped the switch to save you?
In my country this is wrong. It's in the law. I don't know if it's the same for you.